Residual Stress Prediction in Letterbox-Type Repair Welds

Abstract

Many researchers over the last two decades have paid attention to predict satisfactorily the residual stresses in weldments. Dong et al [1] inferred that residual stresses in weld repairs typically exhibit strong three-dimensional features, depending on both component and repair geometry. Repair welds are a common way in industry of repairing cracks or other forms of defects in steel components and structures. Part of the metal is excavated through machining and with it the crack. The groove, which has usually a letterbox geometry, is filled with weld metal of the same composition as the parent material. Since the welding procedure is of a multi-pass type, a repair weld is considered an extreme case (many passes) of a multi-pass weld. Robinson et al [2] concentrated on practical weld repair procedures for low alloy steels. During the design phase of structures and their components or during evaluation of a potential crack initiation and growth, it is important to have a complete description of the residual stress distribution. Moreover, there is the potential for stress distributions to become even more complicated, when weld repairs are undertaken within regions of components that have been fabricated previously by welding. Indeed, in the construction of new plants and for their continued operation, local repair welds are undertaken, so it is necessary to be able to underwrite these for safe operation. As a consequence, knowledge of the residual stresses and their distribution is an important input to an overall structural integrity assessment. Several researchers have conducted numerical analyses incorporating PWHT and creep effects in their models. The main scope of these studies is the examination of hot-cracking risk during the PWHT or during the operation under real conditions. Hyde et al [3] using a lumped bead 3D finite element model to simulate a pressurized CrMoV pipe.